Plating process enhanced by squeegee roller apparatus

ABSTRACT

An improved apparatus for treating plate-like work pieces with a designated chemical solution, including printed circuit boards, including (1) a tank for holding the chemicals, agitation frame and roller assembly, (2) a frame that holds two rollers covered in brush or sponge like material, (3) a guide rail assembly attached to a roller frame, (4) a slotted block attached to a guide rail (5) a disk with a bottom shaft coupling and top pin to move slotted block, (6) a low rpm motor that attaches to disk coupling.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to equipment for coating andelectroplating objects. More particular, this invention relates to anapparatus for coating and electroplating objects such as printed circuitboards.

2. Description of the Related Art

The plating of objects such as printed circuit boards (PCBs), maybeaccomplished by various processes. For PCBs having various holes, aninitial step is required to provide a conductive electrical path on thewhole surface.

This metal deposition process often called “electroless plating”, doesnot rely on the typical electric fields associated with electroplating.Therefore, this metal deposition step is generally harder to controlthan a regular electroplating process.

Since it is impossible to build up a desired level of metal with thisprocess, the object is moved to an electroplating process for additionalbuild up of conductive material to the surface and holes of the object.

In a standard deposition process, the object to be coated is immersedinto various chemical solutions. The tanks, which hold these solutions,have open tops to allow work to be placed inside vertically (i.e., withtheir printed surfaces and direction of the axis of their holes facingsideward).

One of the most commonly used electroplating processes for addingconductive material to objects is an electrolyte plating type process.It involves an open tank filled with plating solution or electrolyte.

These tanks sometimes include electrodes where a voltage is applied toset up an electric field in the tank. A power supply that has a variablevoltage and amperage control is used to create the voltage between theelectrodes

The object to be plated is called the cathode. It is attached to thenegative side of the power supply. The other electrode, called theanode, is attached to the positive terminal of a power supply.

The electrolyte consists of chemicals, usually a metal dissolved andsuspended in a liquid as a metal ion. When the electric field isapplied, the metal ions deposit on the cathode and increase itsthickness over time until the process is halted or the solution isexhausted. If the liquid has no movement or agitation the rate of metalion deposition will slow down by an order of magnitude unless theelectrolyte is agitated or some other means is used to deliver freshelectrolyte.

Agitation is also used to dislodge and sweep away hydrogen gas bubblesthat form on plating objects. Also it is used as a means to moveelectrolyte into sideward holes.

Thus it often proves to be the case that such electroplating processhave the same disadvantages as previously seen for the metal depositionprocess, i.e., their capabilities are limited when it comes todepositing conductive coatings on objects in a vertical tank, withsideward facing holes to be plated.

Because off these disadvantages, there exists a continuing need forimproved metal deposition and electroplating methods and apparatus.

3. Objects and Advantages

There has been summarized above, rather broadly, the prior art that isrelated to the present invention in order that the context of thepresent invention may be better understood and appreciated. In thisregard, it is instructive to also consider the objects and advantages ofthe present invention.

It is an object of the present invention to provide an apparatus thatyields more efficient plating of objects.

It is an object of the present invention to provide an apparatus thatelectroplates tiny sideward facing holes, e.g., printed circuit boards.

It is an object of the present invention to provide an apparatus foreliminating chemical air agitation units that are harmful to people andthe environment.

It is an object of the present invention to provide an apparatus thatselectively plates more inside the hole than surface of the objects,e.g., PCBs.

These and other objects and advantages of the present invention willbecome readily apparent as the invention is better understood byreference to the accompanying summary, drawings and the detaileddescription that follows.

SUMMARY OF THE INVENTION

The present invention is generally directed to satisfying the needs setforth above and overcoming the limitations and problems identified withprior metal deposition and electroplating processes that utilizevertical tanks.

In accordance with one preferred embodiment, the present invention takesthe form of an apparatus for treating plate-like pieces with adesignated chemical solution, including printed circuit boards.

This apparatus includes: (1) a tank for holding the chemical solution,which is configured to receive a vertically oriented work piece, (2) aconductive plating rack configured to receive and mount the work pieceso that the work piece may act as a cathode when the rack is immersed inthe tray and surrounded by an electrolytic solution, (3) a sponge typematerial covering a roller assembly, with a frame to which the rollersare attached and able to move freely, (5) a guide rail attached to aroller assembly, (6) a disk with attachment pin that travels betweenslotted guide block that connects to guide rails for roller assemblymovement, (7) a low rpm motor that is attached with a cam to a disk forguide block travel between disk pin.

There has been summarized above, rather broadly, the present inventionin order that the detailed description that follows may be betterunderstood and appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a perspective view of the tank assembly used with apreferred embodiment of a plating apparatus of the present invention.

FIG. 2 illustrates a roller assembly adjustment for use between objectsto be plated.

FIG. 3 illustrates a roller guide or block used to hold support rail inplace.

FIG. 4 illustrates a roller core fabricated from plastic or inertconductive material with bushings and a sponge like material coveringfor use with the present invention.

FIG. 5 illustrates a tank assembly used for multiple objects to beplated.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purpose of explanation and not limitation, specific details areset forth below in order to provide a thorough understanding of thepresent invention. However, it will be apparent to one skilled in theart the present invention may be practiced in other embodiments thatdepart from these specific details. In other instances, detaileddescriptions of well known methods hardware, ect. are omitted so as notto obscure the description of the present invention with unnecessarydetail.

referring now to the drawing which show a preferred embodiment of thepresent invention and wherein like reference numerals designate likeelements throughout.

FIG. 1 is seen to provide a perspective view of a key aspect of apreferred embodiment of the plating method of the present invention fortreating thin, porous, plate-like work pieces (e.g., PCB).

The materials to be treated, which for illustrative purposes we take tobe PCBs 2, are positioned vertically. FIG. 1 illustrates a clampingdevice 3, having thumb screws 3 a, which is suitable for this purpose.Roller assembly frame 4 is used to hold roller core 5 which isfabricated from plastic or conductive inert or soluble material heldsecurely in place.

The roller assembly is then transported back and forth by means of amotor 6 attached to a disk 7 with an adjustable pin 8 on top is aslotted travel block 9 which connects to a guide bar 10, attached to anadditional top guide bar 11 that travels between guide block 12. Theguide bars are connected to the roller frame 4.

Because of the different types and thickness of objects to be platedthere is an adjustable roller gauge 13 to compensate for varying boardthickness or roller material 14 thickness.

To further improve the travel of the guide rail assembly a guide blockwill be used 15 with a free moving travel wheel. Additionally bushings17 will be added into roller core at either end to allow spinning.Roller will be covered with PVA sponge like material or polypropylenethat acts as a brush and squeegee to coat surface and interior ofobject.

In another preferred embodiment of the present invention, a large tankwith a dual roller assembly 18 will be used for multiple object coating.

1. An apparatus for treating plate-like work pieces with a designatedchemical solution. Including printed circuit boards, said apparatuscomprising: A tank for holding said chemicals, an agitation frame withroller assembly, said tank having an open top which is configured toreceive said work piece when said work piece is oriented so that itslargest-surface area is oriented vertically.
 2. An apparatus as recitedin claim 1, further comprising: A clamping device for electricalconnection and aligning work piece surface.
 3. An apparatus as cited inclaim 1 further comprising a roller brush assembly configured to travelbetween said work piece.
 4. An apparatus cited in claim 3, that furtherincludes a roller core that is conductive and acts as an anode forproducing an electric field.
 5. An apparatus as cited in claim 3,wherein said roller brush assembly is attached to a guide rail that ismoveable and allows travel back and forth.
 6. An apparatus as cited inclaim 5, wherein a guide rail is attached to a slotted block that ridesbetween a pin.
 7. An apparatus as cited in claim 6, wherein a circulardisk with a pivot pin is mounted on top coupled to a low rpm adjustablemotor to drive slotted block and rail assembly.